The invention relates to a composition for dyeing keratin fibres, and in particular human keratin fibres such as the hair, comprising, in a medium which is suitable for dyeing, at least one suitably selected cationic direct dye and at least one nitrobenzene direct dye, as well as to the dyeing process using this composition.
It is well known to dye keratin fibres, and in particular human hair, with dye compositions containing direct dyes and in particular nitrobenzene direct dyes. However, direct dyes have the drawback, when they are incorporated into dye compositions, of leading to colorations which have insufficient staying power, in particular with regard to shampooing.
The Applicant has now discovered that it is possible to obtain novel dyes capable of leading to intense, unselective colorations which show good resistance to the various attacking factors to which the hair may be subjected, by combining at least one suitably selected cationic direct dye and at least one nitrobenzene direct dye.
This discovery forms the basis of the present invention.
A first subject of the invention is thus a ready-to-use composition for dyeing keratin fibres, and in particular human keratin fibres such as the hair, characterized in that it comprises, in a medium which is suitable for dyeing:
at least one cationic direct dye chosen from:
a) the compounds of formula (I) below: 
in which:
D represents a nitrogen atom or a xe2x80x94CH group,
R1 and R2, which may be identical or different, represent a hydrogen atom; a C1-C4 alkyl radical which can be substituted with a xe2x80x94CN, xe2x80x94OH or xe2x80x94NH2 radical; or form, with a carbon atom of the benzene ring, an optionally oxygenated or nitrogenous heterocycle which can be substituted with one or more C1-C4 alkyl radicals; a 4xe2x80x2-aminophenyl radical,
R3 and Rxe2x80x23, which may be identical or different, represent a hydrogen or halogen atom chosen from chlorine, bromine, iodine and fluorine, or a cyano, C1-C4 alkoxy or acetyloxy radical,
Xxe2x88x92 represents an anion preferably chosen from chloride, methyl sulphate and acetate,
A represents a group chosen by structures A1 to A19 below: 
in which R4 represents a C1-C4 alkyl radical which can be substituted with a hydroxyl radical and R5 represents a C1-C4 alkoxy radical, with the proviso that when D represents xe2x80x94CH, when A represents A4 or A13 and when R3 is other than an alkoxy radical, then R1 and R2 do not simultaneously denote a hydrogen atom;
b) the compounds of formula (II) below: 
in which:
R6 represents a hydrogen atom or a C1-C4 alkyl radical,
R7 represents a hydrogen atom, an alkyl radical which can be substituted with a xe2x80x94CN radical or with an amino group, a 4xe2x80x2-aminophenyl radical, or forms, with R6, an optionally oxygenated and/or nitrogenous heterocycle which can be substituted with a C1-C4 alkyl radical,
R8 and R9, which may be identical or different, represent a hydrogen atom, a halogen atom such as bromine, chlorine, iodine or fluorine, a C1-C4 alkyl or C1-C4 alkoxy radical or a xe2x80x94CN radical,
Xxe2x88x92 represents an anion preferably chosen from chloride, methyl sulphate and acetate,
B represents a group chosen by structures B1 to B6 below: 
in which R10 represents a C1-C4 alkyl radical, R11 and R12, which may be identical or different, represent a hydrogen atom or a C1-C4 alkyl radical;
c) the compounds of formulae (III) and (IIIxe2x80x2) below: 
in which:
R13 represents a hydrogen atom, a C1-C4 alkoxy radical, a halogen atom such as bromine, chlorine, iodine or fluorine or an amino radical,
R14 represents a hydrogen atom, a C1-C4 alkyl radical, or forms, with a carbon atom of the benzene ring, a heterocycle which is optionally oxygenated and/or substituted with one or more C1-C4 alkyl groups,
R15 represents a hydrogen or halogen atom such as bromine, chlorine, iodine or fluorine,
R16 and R17, which may be identical or different, represent a hydrogen atom or a C1-C4 alkyl radical,
D1 and D2, which may be identical or different, represent a nitrogen atom or a xe2x80x94CH group,
m=0 or 1,
it being understood that when R13 represents an unsubstituted amino group, then D1 and D2 simultaneously represent a xe2x80x94CH group and m=0,
Xxe2x88x92 represents an anion preferably chosen from chloride, methyl sulphate and acetate,
E represents a group chosen by structures E1 to E8 below: 
in which Rxe2x80x2 represents a C1-C4 alkyl radical; when m=0 and when D1 represents a nitrogen atom, then E can also denote a group of structure E9 below: 
in which Rxe2x80x2 represents a C1-C4 alkyl radical,
and at least one nitrobenzene direct dye.
The ready-to-use dye composition in accordance with the invention leads to intense, chromatic colorations which show low selectivity and excellent properties of resistance both with respect to atmospheric agents such as light and bad weather and with respect to perspiration and the various treatments to which the hair may be subjected (washing, permanent-waving).
A subject of the invention is also a process for dyeing keratin fibres using this ready-to-use dye composition.
The cationic direct dyes of formulae (I), (II), (III) and (IIIxe2x80x2) which can be used in the ready-to-use dye compositions in accordance with the invention are known compounds and are described, for example, in patent applications WO 95/01772, WO 95/15144 and EP-A-0,714,954.
Among the cationic direct dyes of formula (I) which can be used in the ready-to-use dye compositions in accordance with the invention, mention may be made more particularly of the compounds corresponding to structures (I1) to (I52) below: 
Among the compounds of structures (I1) to (I52) described above, the compounds most particularly preferred are those corresponding to structures (I1), (I2), (I14) and (I31).
Among the cationic direct dyes of formula (II) which can be used in the ready-to-use dye compositions in accordance with the invention, mention may be made more particularly of the compounds corresponding to structures (II1) to (II12) below: 
Among the cationic direct dyes of formula (III) which can be used in the ready-to-use dye compositions in accordance with the invention, mention may be made more particularly of the compounds corresponding to structures (III1) to (III18) below: 
Among the specific compounds of structures (III1) to (III18) described above, the compounds most particularly preferred are those corresponding to structures (III4), (III5) and (III13).
Among the cationic direct dyes of formula (IIIxe2x80x2) which can be used in the ready-to-use dye compositions in accordance with the invention, mention may be made more particularly of the compounds corresponding to structures (IIIxe2x80x21) to (IIIxe2x80x23) below: 
The cationic direct dye(s) used according to the invention preferably represent(s) from 0.001 to 10% by weight approximately relative to the total weight of the ready-to-use dye composition, and even more preferably from 0.05 to 5% by weight approximately relative to this weight.
The nitrobenzene direct dye(s) which can be used in the ready-to-use dye composition in accordance with the invention is (are) preferably chosen from the compounds of formula (IV) below: 
in which:
R18 represents an amino radical; an amino radical monosubstituted or disubstituted with a C1-C4 alkyl, C1-C4 monohydroxyalkyl, C2-C4 polyhydroxyalkyl, C1-C4 aminoalkyl, mono(C1-C4) alkylamino(C1-C4) alkyl, di(C1-C4)alkylamino(C1-C4)alkyl or ureido(C1-C4)alkyl or aryl radical or an aryl radical in which the aryl ring is substituted with one or more hydroxyl, carboxyl, amino or di(C1-C4)alkylamino radicals,
R19 represents a hydrogen atom; an amino radical; hydroxyl radical; C1-C4 alkyl radical; C1-C4 alkoxy radical; C1-C4 monohydroxyalkyl radical; C2-C4 polyhydroxyalkyl radical; C1-C4 monohydroxyalkoxy radical; C2-C4 polyhydroxyalkoxy radical; C1-C4 aminoalkoxy radical; an amino radical monosubstituted or disubstituted with a C1-C4 alkyl, C1-C4 monchydroxyalkyl, C2-C4 polyhydroxyalkyl, C1-C4 aminoalkyl, mono (C1-C4) alkylamino(C1-C4)alkyl, di(C1-C4)alkylamino(C1-C4)alkyl or ureido(C1-C4)alkyl or aryl radical or an aryl radical in which the aryl ring is substituted with one or more hydroxyl, carboxyl, amino or di(C1-C4)alkylamino radicals;
R20 represents a hydrogen or halogen atom, a C1-C4 alkyl radical or a nitro group.
Among the nitrobenzene dyes of formula (IV) above, mention may be made most particularly of:
2-amino-4-methyl-5-N-(xcex2-hydroxyethyl)aminonitro-benzene,
4-N-(xcex2-ureidoethyl)aminonitrobenzene,
4-(N-ethyl-N-xcex2-hydroxyethyl)amino-1-N-(xcex2-hydroxy-ethyl)aminonitrobenzene,
2-N-(xcex2-hydroxyethyl)amino-5-methylnitrobenzene,
5-chloro-3-N-(ethyl)amino-4-hydroxynitrobenzene,
5-amino-3-chloro-4-hydroxynitrobenzene,
2-N-(xcex3-hydroxypropyl)amino-5-N,N-bis(xcex2-hydroxyethyl)-aminonitrobenzene,
5-hydroxy-2-N-(xcex3-hydroxypropyl)aminonitrobenzene,
1,3-bis(xcex2-hydroxyethyl)amino-4-chloro-6-nitrobenzene,
2,4-diaminonitrobenzene,
3,4-diaminonitrobenzene,
2,5-diaminonitrobenzene,
3-amino-4-hydroxynitrobenzene,
4-amino-3-hydroxynitrobenzene,
5-amino-2-hydroxynitrobenzene,
2-amino-5-hydroxynitrobenzene,
4-amino-3-hydroxynitrobenzene,
5-amino-2-hydroxynitrobenzene,
2-amino-3-hydroxynitrobenzene,
2-amino-5-N-(xcex2-hydroxyethyl)aminonitrobenzene,
2-amino-5-N,N-bis(xcex2-hydroxyethyl)aminonitrobenzene,
2,5-N,Nxe2x80x2-(xcex2-hydroxyethyl)aminonitrobenzene,
2-N-(xcex2-hydroxyethyl)amino-5-N,N-bis(xcex2-hydroxyethyl)-aminonitrobenzene,
2-amino-5-N-(methyl)aminonitrobenzene,
2-N-(methyl)amino-5-N,N-bis(xcex2-hydroxyethyl)aminonitrobenzene,
2-N-(methyl)amino-5-(N-methyl-N-xcex2-hydroxyethyl)aminonitrobenzene,
2,5-N,Nxe2x80x2-(xcex2-hydroxyethyl)aminonitrobenzene,
2-N-(xcex2-hydroxyethyl)amino-5-hydroxynitrobenzene,
3-methoxy-4-N-(xcex2-hydroxyethyl)aminonitrobenzene,
2-N-(methyl)amino-4-xcex2-hydroxyethyloxynitrobenzene,
2-amino-3-methylnitrobenzene,
2-N-(xcex2-hydroxyethyl)amino-5-aminonitrobenzene,
2-amino-4-chloro-5-N-(xcex2-hydroxyethyl)aminonitrobenzene,
2-amino-4-methyl-5-N-(xcex2-hydroxyethyl)aminonitrobenzene,
2-amino-4-methyl-5-N-(methyl)aminonitrobenzene,
2-N-(xcex2-hydroxyethyl)amino-5-methoxynitrobenzene,
2-amino-5-xcex2-hydroxyethyloxynitrobenzene,
2-N-(xcex2-hydroxyethyl)aminonitrobenzene,
3-amino-4-N-(xcex2-hydroxyethyl)aminonitrobenzene,
3-xcex2-hydroxyethyloxy-4-N-(xcex2-hydroxyethyl)aminonitrobenzene,
2-N-(methyl)amino-4-xcex2,xcex3-dihydroxypropyloxynitrobenzene,
2-N-(xcex2-hydroxyethyl)amino-5-xcex2-hydroxyethyloxynitrobenzene,
2-N-(xcex2-hydroxyethyl)amino-5-xcex2,xcex3-dihydroxypropyloxynitrobenzene,
2-hydroxy-4-N-(xcex2-hydroxyethyl)aminonitrobenzene,
2-N-(methyl)amino-4-methyl-5-aminonitrobenzene,
2-amino-4-isopropyl-5-N-(methyl)aminonitrobenzene,
2-N-(methyl)amino-5-(N-methyl-N-xcex2,xcex3-dihydroxypropyl)aminonitrobenzene,
3-N-(xcex2-hydroxyethyl)amino-4-N-(xcex2-hydroxyethyl)aminonitrobenzene,
2-amino-4-methyl-5-N-(xcex2,xcex3-dihydroxypropyl)aminonitrobenzene,
2-amino-4-methyl-5-hydroxynitrobenzene,
2-N-(xcex2-hydroxyethyl)amino-4-N-(xcex2-hydroxyethyl)aminonitrobenzene,
2-amino-5-N-(xcex2-aminoethyl)aminonitrobenzene,
2-N-(xcex2-aminoethyl)amino-5-methoxynitrobenzene,
2-N-(methyl)amino-5-N-(xcex2-aminoethyl)aminonitrobenzene,
2-N-(xcex2-aminoethyl)amino-4-N,N-(dimethyl)aminonitrobenzene,
3-amino-4-N-(xcex2-aminoethyl)aminonitrobenzene,
2-amino-4-methyl-5-N-(xcex2-aminoethyl)aminonitrobenzene,
2-N-(xcex2-aminoethyl)amino-5-N,N-bis(xcex2-hydroxyethyl)aminonitrobenzene,
3-xcex2-aminoethyloxy-4-aminonitrobenzene,
2-N-(methyl)amino-5-(N-xcex4-amino-n-butyl)aminonitrobenzene,
2-N-(xcex3-amino-n-propyl)amino-5-N,N-(dimethyl)aminonitrobenzene,
3-methoxy-4-N-(xcex2-aminoethyl)aminonitrobenzene,
2-N-(xcex2-aminoethyl)amino-5-aminonitrobenzene,
2-amino-4-chloro-5-N-(xcex2-aminoethyl)aminonitrobenzene,
2-N-(xcex2-aminoethyl)amino-4-methoxynitrobenzene,
2-N-(xcex2-aminoethyl)aminonitrobenzene,
2-N-(xcex2-aminoethyl)amino-5-N-(xcex2-aminoethyl)aminonitrobenzene,
2-N-(xcex2-aminoethyl)amino-4-xcex2-hydroxyethyloxynitrobenzene,
3-xcex2-hydroxyethyloxy-4-N-(xcex2-aminoethyl)aminonitrobenzene,
2-amino-5-aminoethyloxynitrobenzene,
3-hydroxy-4-N-(xcex2-aminoethyl)aminonitrobenzene,
2-N-(xcex2-aminoethyl)amino-5-xcex2-hydroxyethyloxynitrobenzene,
2-N-(xcex2-aminoethyl)amino-4-hydroxynitrobenzene,
2-{[2-hydroxy-3-N-(xcex2-hydroxyethyl)amino-6-nitro]benzyloxy}ethylamine, and
2-{[2-hydroxy-3-N-(xcex2-hydroxypropyl)amino-6-nitro]benzyloxy}ethylamine.
Among the nitrobenzene dyes of formula (IV) above, the ones most particularly preferred are:
2-amino-4-methyl-5-N-(xcex2-hydroxyethyl)aminonitrobenzene,
4-N-(xcex2-ureidoethyl)aminonitrobenzene,
4-(N-ethyl-N-xcex2-hydroxyethyl)amino-1-N-(xcex2-hydroxyethyl)aminonitrobenzene,
2-N-(xcex2-hydroxyethyl)amino-5-methylnitrobenzene,
5-chloro-3-N-(ethyl)amino-4-hydroxynitrobenzene,
5-amino-3-chloro-4-hydroxynitrobenzene,
2-N-(xcex3-hydroxypropyl)amino-5-N,N-bis(xcex2-hydroxyethyl)-aminonitrobenzene,
5-hydroxy-2-N-(xcex3-hydroxypropyl)aminonitrobenzene,
1,3-bis(xcex2-hydroxyethyl)amino-4-chloro-6-nitrobenzene,
3,4-diaminonitrobenzene,
2-amino-5-hydroxynitrobenzene,
2-amino-3-hydroxynitrobenzene,
2-amino-5-N-(xcex2-hydroxyethyl)aminonitrobenzene,
2-amino-5-N,N-bis(xcex2-hydroxyethyl)aminonitrobenzene,
2-N-(xcex2-hydroxyethyl)amino-5-N,N-bis(xcex2-hydroxyethyl)-aminonitrobenzene,
2-N-(xcex2-hydroxyethyl)amino-5-hydroxynitrobenzene,
2-N-(xcex2-hydroxyethyl)amino-5-aminonitrobenzene,
2-N-(xcex2-aminoethyl) amino-4-methoxynitrobenzene, and
2-N-(xcex2-aminoethyl)amino-5-xcex2-hydroxyethyloxynitro-benzene
The nitrobenzene dye(s) preferably represent(s) from 0.0005 to 15% by weight approximately relative to the total weight of the ready-to-use dye composition in accordance with the invention, and even more preferably from 0.005 to 10% by weight approximately relative to this weight.
The ready-to-use dye composition in accordance with the invention can also contain one or more oxidation bases and/or one or more couplers. These oxidation bases can be chosen in particular from para-phenylenediamines, para-aminophenols, ortho-phenylenediamines and heterocyclic bases such as, for example, pyridine derivatives, pyrimidine derivatives, pyrazole derivatives and pyrazolopyrimidine derivatives. The couplers can be chosen in particular from meta-phenylenediamines, meta-aminophenols, meta-diphenols, heterocyclic couplers such as, for example, indole derivatives, indoline derivatives, benzimidazole derivatives, benzomorpholine derivatives, sesamol derivatives, pyridine, pyrimidine and pyrazole derivatives, and the addition salts thereof with an acid.
When they are present, the oxidation base(s) preferably represent(s) from 0.0005 to 12% by weight approximately relative to the total weight of the dye composition in accordance with the invention, and even more preferably from 0.005 to 8% by weight approximately relative to this weight.
When they are present, the coupler(s) preferably represent(s) from 0.0001 to 10% by weight approximately relative to the total weight of the ready-to-use dye composition, and even more preferably from 0.005 to 5% by weight approximately relative to this weight.
In general, the addition salts with an acid which can be used in the context of the dye compositions of the invention (oxidation bases and couplers) are chosen in particular from the hydrochlorides, hydrobromides, sulphates, tartrates, lactates and acetates.
When one or more oxidation bases and/or one or more couplers are used, the ready-to-use dye composition can then also contain at least one oxidizing agent chosen, for example, from hydrogen peroxide, urea peroxide, alkali metal bromates, persalts such as perborates and persulphates, and enzymes such as peroxidases and two-electron oxidoreductases.
Among the 2-electron oxidoreductases which can be used as oxidizing agents in the ready-to-use dye composition in accordance with the invention, mention may be made more particularly of pyranose oxidases, glucose oxidases, glycerol oxidases, lactate oxidases, pyruvate oxidases and uricases.
According to the invention, the use of uricases of animal, microbiological or biotechnological origin is particularly preferred.
By way of example, mention may be made in particular of the uricase extracted from boar liver, the uricase from Arthrobacter globiformis and the uricase from Aspergillus flavus. 
The 2-electron oxidoreductase(s) can be used in pure crystalline form or in a form diluted in a diluent which is inert with respect to the said 2-electron oxidoreductase.
When they are used, the 2-electron oxidoreductase(s) preferably represent(s) from 0.01 to 20% by weight approximately relative to the total weight of the ready-to-use dye composition, and even more preferably from 0.1 to 5% by weight approximately relative to this weight.
When an enzyme of 2-electron oxidoreductase type is used in accordance with the invention, the ready-to-use dye composition can also contain one or more donors for the said enzyme.
According to the invention, the term xe2x80x9cdonorxe2x80x9d refers to the various substrates involved in the functioning of the said 2-electron oxidoreductase(s).
The nature of the donor (or substrate) used varies as a function of the nature of the 2-electron oxidoreductase which is used. For example, D-glucose, L-sorbose and D-xylose may be mentioned as donors for pyranose oxidases; D-glucose may be mentioned as a donor for glucose oxidases; glycerol and dihydroxyacetone may be mentioned as donors for glycerol oxidases; lactic acid and its salts may be mentioned as donors for lactate oxidases; pyruvic acid and its salts may be mentioned as donors for pyruvate oxidases; and lastly, uric acid and its salts may be mentioned as donors for uricases.
When they are used, the donor(s) (or substrate(s)) preferably represent(s) from 0.01 to 20% by weight approximately relative to the total weight of the ready-to-use dye composition in accordance with the invention, and even more preferably from 0.1 to 5% approximately relative to this weight.
The medium which is suitable for dyeing (or support) for the ready-to-use dye composition in accordance with the invention generally consists of water or of a mixture of water and at least one organic solvent to dissolve the compounds which would not be sufficiently water-soluble. As organic solvents, mention may be made, for example, of C1-C4 alkanols, such as ethanol and isopropanol, as well as aromatic alcohols such as benzyl alcohol or phenoxyethanol, similar products and mixtures thereof.
The pH of the ready-to-use dye composition in accordance with the invention is generally between 5 and 11 approximately and preferably between 6.5 and 10 approximately. It can be adjusted to the desired value by means of acidifying or basifying agents usually used for dyeing keratin fibres.
Among the acidifying agents, mentioned may be made, by way of example, of inorganic or organic acids such as hydrochloric acid, orthophosphoric acid, sulphuric acid, carboxylic acids such as acetic acid, tartaric acid, citric acid and lactic acid, and sulphonic acids.
Among the basifying agents, mention may be made, by way of example, of aqueous ammonia, alkaline carbonates, alkanolamines such as mono-, di- and triethanolamine, 2-methyl-2-amino-1-propanol and derivatives thereof, sodium hydroxide, potassium hydroxide and the compounds of formula (V) below: 
in which W is a propylene residue optionally substituted with a hydroxyl group or a C1-C4 alkyl radical; R21, R22, R23 and R24, which may be identical or different, represent a hydrogen atom or a C1-C4 alkyl or C1-C4 hydroxyalkyl radical.
The ready-to-use dye composition in accordance with the invention can also contain various adjuvants conventionally used in compositions for dyeing the hair, such as, for example, antioxidants, penetrating agents, sequestering agents, fragrances, buffers, dispersing agents, film-forming agents, preserving agents and opacifiers.
Needless to say, a person skilled in the art will take care to select this or these optional complementary compounds such that the advantageous properties intrinsically associated with the ready-to-use dye composition in accordance with the invention are not, or are not substantially, adversely affected by the addition(s) envisaged.
The ready-to-use dye composition in accordance with the invention can be in various forms, such as in the form of liquids, creams or gels, which may be pressurized, or in any other form which is suitable for dyeing keratin fibres, and in particular human hair.
When the ready-to-use dye composition in accordance with the invention contains at least one oxidation base and/or at least one coupler and at least one oxidizing agent, it must then be free of gaseous oxygen, so as to avoid any premature oxidation of the oxidation dye(s).
A subject of the invention is also a process for dyeing keratin fibres, and in particular human keratin fibres such as the hair, using the ready-to-use dye composition as defined above.
According to this process, at least one ready-to-use dye composition as defined above is applied to the fibres, for a period which is sufficient to develop the desired coloration, after which the fibres are rinsed, optionally washed with shampoo, rinsed again and dried.
The time required to develop the coloration on the keratin fibres is generally between 3 and 60 minutes and even more precisely between 5 and 40 minutes.
According to one specific embodiment of the invention, and when the dye composition in accordance with the invention contains at least one oxidation base and/or at least one coupler, the process includes a preliminary step which consists in separately storing, on the one hand, a composition (A) comprising, in a medium which is suitable for dyeing, at least one cationic direct dye as defined above, at least one nitrobenzene direct dye and at least one oxidation base and/or at least one coupler, and, on the other hand, a composition (B) containing, in a medium which is suitable for dyeing, at least one oxidizing agent, and then in mixing them together at the time of use, before applying this mixture to the keratin fibres.
Another subject of the invention is a multi-compartment dyeing device or xe2x80x9ckitxe2x80x9d or any other multi-compartment packaging system, a first compartment of which contains composition (A) as defined above and a second compartment of which contains composition (B) as defined above. These devices can be equipped with a means for applying the desired mixture to the hair, such as the devices described in patent FR-2,586,913 in the name of the Applicant.
The examples which follow are intended to illustrate the invention without, however, limiting its scope.